A fuel vapor pressure management apparatus that manages pressure and detects leaks in a fuel system. In particular, a fuel vapor pressure management apparatus that vents positive pressure, vents excess negative pressure, and uses evaporative natural vacuum to perform a leak diagnostic.
Conventional fuel systems for vehicles with internal combustion engines can include a canister that accumulates fuel vapor from a headspace of a fuel tank. If there is a leak in the fuel tank, the canister, or any other component of the fuel system, fuel vapor could escape through the leak and be released into the atmosphere instead of being accumulated in the canister. Various government regulatory agencies, e.g., the U.S. Environmental Protection Agency and the Air Resources Board of the California Environmental Protection Agency, have promulgated standards related to limiting fuel vapor releases into the atmosphere. Thus, it is believed that there is a need to avoid releasing fuel vapors into the atmosphere, and to provide an-apparatus and a method for performing a leak diagnostic, so as to comply with these standards.
In such conventional fuel systems, excess fuel vapor can accumulate immediately after engine shutdown, thereby creating a positive pressure in the fuel vapor pressure management system. Excess negative pressure in closed fuel systems can occur under some operating and atmospheric conditions, thereby causing stress on components of these fuel systems. Thus, it is believed that there is a need to vent, or xe2x80x9cblow-off,xe2x80x9d the positive pressure, and to vent, or xe2x80x9crelieve,xe2x80x9d the excess negative pressure. Similarly, it is also believed to be desirable to relieve excess positive pressure that can occur during tank refueling. Thus, it is believed that there is a need to allow air, but not fuel vapor, to exit the tank at high flow rates during tank refueling. This is commonly referred to as onboard refueling vapor recovery (ORVR).
The present invention provides a fuel vapor pressure management apparatus that includes a housing and a pressure operable device. The housing defines an interior chamber and includes first and second ports that communicate with the interior chamber. The pressure operable device separates the interior chamber into a first portion in fluid communication with the first port and a second portion in fluid communication with a second port. The pressure operable device includes a poppet that is movable along an axis, and a seal that is adapted to cooperatively engage the poppet. A first arrangement of the pressure operable device occurs when there is a first negative pressure level at the first port relative to the second port, and the seal is in a first deformed configuration. A second arrangement of the pressure operable device permits a first fluid flow from the second port to the first port when the seal is in a second deformed configuration. And a third arrangement of the pressure operable device permits a second fluid flow from the first port to the second port when the seal is in an undeformed configuration.
The present invention also provides a fuel vapor pressure management apparatus that includes a housing that defines an interior chamber, and a pressure operable device that occupies a first space in the interior chamber. The housing and the interior chamber occupy a volume less than 240 cubic centimeters. The pressure operable device performs a leak diagnostic based on a negative pressure at a first pressure level, relieves negative pressure below the first pressure level, and blows-off positive pressure above a second pressure level.